The assumption from Apple is that if you are going to order a machine with 4 graphics cards you know what you're doing it for! Even if they operated in SLI, 4 7300s would only be a little faster than the ATI 1900 they offer and probably slower than an 8800 GTX...Thought it might be actually. Strange how their is no mention of octo-monitors on the Apple site...
Thats possible over the pci express bus on the lower cards, you only need the crossover patch with the faster cards, it was enabled in software a while backSLI Works under Windows on the mac pro!
Some guys over at Appleinsider got it working.
In OS X however, that's a big no-go.
LOL I saw 700£ and was confused, then I saw that the setup didn't come with any monitors. $1400 just for a monitor stand. Remarkable.